1. Technical Field
The invention relates to paper alignment for printing devices. More particularly, the invention relates to methods and apparatus for performing paper tray alignment using an alignment calibration page to determine and apply alignment calibration values.
2. Description of the Prior Art
When a new printer is configured, many features and pieces of equipment on the printer need to be set up and adjusted. Paper trays are no exception. For example, a technician could spend several minutes skewing and shifting the paper trays of a printer to ensure accurate registration, which is the precise positioning of printed elements. Ensuring accurate registration is important especially when printing duplex pages, i.e. both sides of pages.
The locations of elements to be printed on a page are typically described in Cartesian coordinates. When printing such elements on a page, the elements may end up with different coordinates than intended for the actual printed page, and sometimes such elements are printed smaller or larger than expected. Such problems arise, for example, when a medium (such as a page) feeding mechanism or drawing device is not precisely calibrated, or when the medium is stretched. Another problem is that sometimes impressions are skewed. Skewed impressions may happen, for instance, when paper trays, paper feeding mechanisms, and drawing devices are not parallel. Yet, another problem is that positions of printed elements are sometimes shifted, for example, towards the left, right, top, and/or bottom of a page.
Corrections to shifted elements are taught in Splash M Series, User""s Manual Version 1.0, Sep. 22, 1998. A Splash M Series Configuration disk supports two page positioning configuration parameters in a DP.INI file: sshift and fshift. These parameters allow adjusting the position of an image with respect to the center of the page. The image can be repositioned in all four directions, up, down, right, and left. sshift adjusts the center of the page along an S axis (slow scan axis) and fshift adjusts the center of the page along an F axis (fast scan axis). The orientation of each of the S and F axes is dependent on the direction the paper is being pulled through the printer. The Splash technique is limited in correcting problems in shifting.
It would be advantageous to provide methods and apparatus to shift, rotate, and scale images to be printed on a page, thereby correcting for a paper tray""s physical inadequacies.
It would be advantageous to provide methods and apparatus for paper tray adjustments that work with other devices, such as, for example, workstations and LCD panels, and with other applications.
It would be advantageous to provide methods and apparatus to calculate parameters for plane rotation and translation by using a test pattern, and whereby the use of any instrument for measuring is not required.
It would be advantageous to provide methods and apparatus to calculate a scaling factor parameter, and whereby only a ruler is needed.
A tray alignment calibration page and method and apparatus using the page are provided. The page is printable using an alignment dialog box. The page has graduated scales with values running along the horizontal and vertical edges. An end user folds the page in half horizontally and vertically to locate the center of the page. The end user also obtains other values, such as scaling factors, from the page. Such values are enterable as correction values into the alignment dialog to align an image to be printed on a target page so that printing occurs centered on the page. A set of input image Cartesian coordinates is mapped to output device Cartesian coordinates, taking into account scaling, rotational, and translation factors. The invention handles duplex printing, as well.